A sliding gate assembly is widely used with various types of molten-metal holding vessels, such as a molten-steel ladle or tundish, by taking advantage of its ability to control the flow volume of molten metal with a high degree of accuracy.
The sliding gate assembly can be generally classified into two types: a two-plate type comprising in combination an upper (fixed) plate and a lower (sliding) plate; and a three-plate type comprising a pair of upper and lower fixed plates and a sliding plate disposed between the fixed plates. The sliding gate assembly includes means for applying a certain sealing pressure or surface pressure onto the opposed sliding surfaces of the plates to prevent the molten metal from entering between the plates, wherein the surface pressure is set at a given value in the range allowing the sliding plate to be adequately operated.
The above surface-pressure applying means typically comprises a coil spring. Further, the sliding gate assembly includes a bolt tightening/loosening mechanism for controlling the loading and releasing of the surface pressure. Generally, the bolt tightening/loosening mechanism obliges an operator to perform a heavy work of tightening or loosening a bolt using a tool in hot environment, and involves a problem of seizure of the bolt
In order to facilitate simplifying the surface-pressure loading/releasing mechanism and enhancing the operationability thereof, various mechanisms have been proposed which utilizes the reciprocating motion of a cylinder to drive a slide frame.
For example, Japanese Patent Laid-Open Publication No. H08-117985 discloses a mechanism in which, in a surface-pressure loading operation, a surface-pressure bar is coupled to a sliding block (slide frame) through a surface-pressure link, and moved in conjunction with a sliding movement of a surface-pressure bar with a slide frame to compress an elastic body so as to load a surface pressure between an upper plate and the sliding plate.
Japanese Patent Laid-Open Publication No. S62-279071 discloses a sliding gate assembly including a surface-pressure loading/releasing mechanism. This mechanism having strong relevance to the present invention will be described with reference to FIGS. 11 to 13. In these figures, the sliding gate assembly comprises an upside frame 51, a suspending frame 52 attached openably to the upside frame 51, a slide frame 53 slidably attached to the suspending frame 52 and adapted to be moved by a driving device (not shown), and a surface-pressure loading/releasing mechanism 54 provided between the upside frame 51 and the suspending frame 52 and adapted to be moved by utilizing a sliding force of the slide frame 53. This surface-pressure loading/releasing mechanism 54 is composes of a pressing member for pressing an elastic body 55 to the suspending frame 52, a pair of hooks 57 for coupling the pressing member 56 to the upside frame 51, a cotter 58 adapted to be detachably inserted into the pressing member 56 in a direction of the center of the sliding gate assembly, and an inclined block provided on the longitudinal side surface of the slide frame 53 and adapted to be brought into slide contact with the inclined block 59 in conjunction with the sliding movement of the slide frame 53. According to the mechanism disclosed in the above publication, when the inclined block 59 is slidingly moved and brought into slide contact with the cotter 58, the elastic body 55 can be compressed. The pressing member 56 is then coupled to the upside frame 51 by the hooks 57 so that the suspending frame 52 is fixed to the upside frame 51 in a close contact manner. Thus, a surface pressure is loaded between the sliding surfaces of upper and lower plates even after the slide frame 53 is moved to release the slide contact between the cotter 58 and the inclined block 59.
However, in the mechanism disclosed in the above Japanese Patent Laid-Open Publication No. S62-279071, after the completion of the surface-pressure loading operation, the cotter must be detached from or pulled out of the pressing member to prevent the contact with the inclined block again. The negligence of the pulling-out operation possibly causes unintentional release of the surface pressure during subsequent operations or an intended open-close operation of the sliding gate assembly due to disengagement of the hook from the pressing member.
The mechanism disclosed in the aforementioned Japanese Patent Laid-Open Publication No. H08-117985 is also required to move the surface-pressure link to a position where it is not engaged with the sliding block (slide frame), after the completion of the surface-pressure loading operation. The negligence of the disengaging operation possibly causes unintentional release of the surface pressure due to the movement of the surface-pressure link in conjunction with the slide frame.
As above, while the conventional mechanisms can load and release the surface pressure in conjunction with the movement of the slide frame to achieve fairly reduced workload, they are still required to move the surface-pressure link or pull out the cotter after the surface-pressure loading operation so as to prevent the surface pressure from being released during a primary operation. In addition, the disengaging operation of the surface-pressure link or the pulling-out operation of the cotter is manually performed, and thus a possible human error can lead to a serious trouble of leakage of molten metal from between the plates due to the accidental release of the surface pressure during the primary operation. Thus, there is still the need for providing an improved surface-pressure loading/releasing mechanism capable of preventing occurrence of a human error and such a trouble.
Other features and advantages of the present invention will be apparent from the accompanying drawings and from the detailed description.